This invention relates to an oxygen stabilized intermetallic compound capable of sorbing hydrogen and other gases. More specifically, this invention relates to an oxygen stabilized intermetallic compound capable of reversibly sorbing hydrogen and of gettering other gases such as CO, N.sub.2 and O.sub.2.
It is generally recognized that impurities in the plasma of magnetic confinement fusion devices such as Tokamaks can seriously limit the performance of such devices by lowering the plasma temperature and quenching the fusion reaction. These impurities are introduced into the plasma by a variety of sputtering and erosion processes occuring at the walls of the devices by hydrogen isotope recycling. These impurities may consist of the elements oxygen, carbon, hydrogen, including deuterium and tritium, and compounds of these elements. Some metal ions may also be present which have been sputtered from the walls of the device during operation.
Some solutions to the problem of impurity control include modifying the recycling processes, minimizing the erosion rates at the surfaces facing the plasma and removing the offending impurities from the plasma. It has been shown that the trapping and subsequent readmission of hydrogen isotopes from walls affects plasma profiles, especially at the edge, substantially modifying impurity influxes. In deuterium-tritium burning devices, wall recycling will strongly influence tritium inventory, which must be held to within well-defined limits. Therefore, tritium retention is an important factor in the design of a suitable fusion device.
There is need for materials which can be placed within a magnetic containment fusion device to getter hydrogen and hydrogen isotopes under the low pressure, high temperature conditions which are present within such device. The material must be reasonably selective for hydrogen and must be able to function as a hydrogen and hydrogen isotope getter at pressures down to at least 10.sup.-6 torr, in the presence of power fluxes up to about 50 w/cm.sup.2 and at temperatures varying from room temperature up to about 200.degree. C. The material should have a high hydrogen capacity to reduce the frequency of regeneration, it should be able to be regenerated with respect to absorbed hydrogen at a relatively low temperature, preferably no higher than 500.degree. C., and it must function as a hydrogen getter in the presence of other contaminant gases. Preferably, the material would getter other gases present in the plasma as as contaminants, such as N.sub.2, O.sub.2 and CO, although it need not be regenerable with respect to these gases. The material must be able to be placed within the device either as a coating on a substrate or applied directly to the walls.
One material which has been used successfully for this purpose is sublimed titanium. However, titanium is not easily regenerated so that fresh layers must be applied to the surface for each gettering cycle. Another material which fulfills many of the requirements is ST101. This material is a proprietary Zr-Al based alloy available from SAES Getters of Milan, Italy. The Zr-Al alloys have limited hydrogen capacities and regeneration of the alloy within a reasonable time period requires that it be heated to temperatures of at least 750.degree. C. A zirconium-vanadium-chromium alloy which meets many of these requirements is disclosed in an U.S. patent application Ser. No. 196,710, filed Oct. 14, 1980 and assigned to the common assignee.